Komeiji Koishi, Sister Satori

Whenever Koishi Komeiji, Sister Satori enters
the battlefield, you gain 4 life and each opponent
loses 4 life. Proliferate. Proliferate.
Koishi Komeiji, Sister Satori phases out on your
end step. Put a +1/+1 counter on this creature
for each time it phases out on your end step.
If Koishi Komeiji, Sister Satori deals combat
damage, you may pay {b}{g}. If you do, double
this creature's power.